The invention relates to optical beam scanning apparatus, and to more particularly to a beam scanner capable of quickly obtaining operating speed so as to avoid the need for keeping the scanner energized on standby power, in an apparatus efficient in construction.
Optical beam scanners have conventionally used various types of scanning devices. Many "dither" scanners have employed an oscillating spring-loaded member for oscillating the position of a scanner mirror. This system required low power, which was necessary because when used in hand-held laser bar code scanners, the ditherer device was kept oscillating on standby power when the laser was inactive and standing by for use. The reason for keeping such scanning apparatus active during intermittent periods of nonuse was the relatively long startup time required to attain full normal oscillating speed after the apparatus was first energized.
Some of the prior systems employed a stepper motor for oscillating a mirror. The motor would step from one stable state to another stable state to effect a sinusoidal mirror oscillation by mass loading. Although such systems were capable of rapid startup, the stepper motor consumed a great deal of power, approximately in the range of 40 to 70 milliamps.
It is an object of the present invention to eliminate the need for continued energization of an optical beam scanner motor on a standby basis, by powering a scanner mechanism with a motor and drawing low power and including a control system that brings the scanner very quickly up to operating speed when power is first applied, by the application of a controlled burst of power to accelerate the motor.